As I understand it, when QGIS is started from qgis.bat some OSGeo4w specific folder paths are prepended to the OS PATH variable. When I do this and go look in Settings>Options>System>Current environment variables>Path I see
If I re-start QGIS using qgis-bin.exe instead and go look at the Path variable, it's the same value. I would have thought that the box would be empty and that the Python console would be interrogating the OS Path-listed instance of Python instead, which on my computer is, in fact, under an ArcGIS Pro folder (this isn't my goal, just part of why I don't understand what qgis.bat is supposed to be doing).
In fact, when I edit the batch file by commenting out the call to py_env.bat, eg.
rem call py3_env.bat
and start again, the Path value is still the same. Why is that?